Analogies Concerning Life 143 



thus spring into corporeal existence, as it 

 were, are essentially closed curves or loops, 

 which cannot be generated ; they can be ex- 

 panded or enlarged to cover a wide field, and 

 they can be contracted or shrunk up into 

 insignificance, but they cannot be created, 

 they must be pre-existent ; they were in the 

 non-magnetised steel all the time, though 

 they were so small and ill-arranged that they 

 had no perceptible effect whatever ; they 

 constituted a potentiality for magnetism ; 

 they existed as molecular closed curves or 

 loops, which, by the operation called 

 magnetisation, could, some of them, be 

 opened out into loops of finite area and 

 spread out into space, where they are called 

 " lines of force." They then constitute the 

 region called a magnetic field, which 

 remains a seat of so-called " permanent " 

 magnetic activity, until by lapse of time, 

 excessive heat, or other circumstance, they 

 close up again ; and so the magnet, as a 

 magnet, dies. The magnetism itself, how- 

 ever, has not really died, it has a perpetual 



